Slips are typically extended by relative movement with respect to an adjacent cone. As the slip element rides up the cone it is moved radially toward a surrounding tubular. The leading face of each slip has a surface treatment commonly referred to as wickers which can be made of a hard material such as tungsten carbide or polycrystalline diamonds to enhance the bite of the slips into the surrounding tubular. Traditionally, slip wickers are made of carburized (heat-treated) steel. Wickers can also be made of high-yield materials coated with tungsten carbide or carbide inserts can be used in place of wickers by affixing them to a base material. Typically the wickers penetrate the inner wall of the pipe to facilitate the grip. Slips commonly anchor isolation devices such as packers and bridge plugs.
The common issue with slips is to get them to release especially after being set a very long time or after being exposed to extreme loading or operating conditions. Typically, force is applied to the slip to try to force the slip to ride down on the cone for a release of the wickers. Sometimes, especially after a long period of being in a set position and in a debris laden environment it becomes difficult to get the slips to release. Sometimes the slips refuse to fully release and a milling operation that is very expensive is needed to enable removal of the associated device.
Prior designs guide the slips at their edges to make sure they don't cock when being extended and to allow them to tangentially transfer radial loading when part of a continuous slip ring. Typical of some of the one piece slip arrangements are: U.S. Pat. No. 4,311,196; GB 2323869; U.S. Pat. Nos. 6,213,204; 5,487,427; 5,174,397; 3,279,544; and 6,241,017. Existing designs also pose an issue with manufacturing complexity and associated cost, both with the slips and supports, as well as the isolation device itself. These designs still present an issue of difficult release and the present invention presents a design to deal with this issue. The design features a two piece construction with a relatively movable base structure allows pulling the base of the assembly out from under the set wicker portion. The two elements move in tandem for a set. The base portion guides the wicker portion above both in the center and the edge of the wicker portion. These and other features of the present invention will be more readily apparent to those skilled in the art from a review of description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.